Andy Goldsworthy sculpture "Hanging Trees" in the Yorkshire Sculpture Park, Wakefield. The tree is built into the walls that surround it. I love Andy Goldsworthy's work - his creations are all made from natural materials, wood, stone, leaves and they are so very memorable.
If anyone gets the chance do go to the Yorkshire Sculpture Park - the exhibition of Andy Goldsworthy's work continues until January, there are loads of other works by Henry Moore and Elizabeth Frink as well.
For more details: http://en.wikipedia.org/wiki/Andy_Goldsworthy